When I was an undergraduate in the early 1970s, I was assigned a classic paper published in Scientific American that began: "There is an experiment in psychology that you can perform easily in your home....Buy two presents for your wife, choosing things ... she will find equally attractive." Just ten years after those words were written, the author's blithe assumption that his readers were male struck me as comically archaic.By the early '70s, women in science were no longer an oddity or a joke but a given. Today, in my own field, the study of language development in children, a majority of the scientists are women. Even in scientific fields with a higher proportion of men, the contributions of women are so indispensable that any talk of turning back the clock would be morally heinous and scientifically ruinous.
Yet to hear the reaction to Harvard President Lawrence Summers's remarks at a conference on gender imbalances in science, in which he raised the possibility of innate sex differences, one might guess that he had proposed exactly that. Nancy Hopkins, the eminent MIT biologist and advocate for women in science, stormed out of the room to avoid, she said, passing out from shock. An engineering dean called his remarks "an intellectual tsunami," and, with equal tastelessness, a Boston Globe columnist compared him to people who utter racial epithets or wear swastikas. Alumnae threatened to withhold donations, and the National Organization of Women called for his resignation. Summers was raked in a letter signed by more than 100 Harvard faculty members and shamed into issuing serial apologies.
Summers did not, of course, say that women are "natively inferior," that "they just can't cut it," that they suffer "an inherent cognitive deficit in the sciences," or that men have "a monopoly on basic math ability," as many academics and journalists assumed. Only a madman could believe such things. Summers's analysis of why there might be fewer women in mathematics and science is commonplace among economists who study gender disparities in employment, though it is rarely mentioned in the press or in academia when it comes to discussions of the gender gap in science and engineering. The fact that women make up only 20 percent of the workforce in science, engineering, and technology development has at least three possible (and not mutually exclusive) explanations. One is the persistence of discrimination, discouragement, and other barriers. In popular discussions of gender imbalances in the workforce, this is the explanation most mentioned. Although no one can deny that women in science still face these injustices, there are reasons to doubt they are the only explanation. A second possibility is that gender disparities can arise in the absence of discrimination as long as men and women differ, on average, in their mixture of talents, temperaments, and interests—whether this difference is the result of biology, socialization, or an interaction of the two. A third explanation is that child-rearing, still disproportionately shouldered by women, does not easily co-exist with professions that demand Herculean commitments of time. These considerations speak against the reflex of attributing every gender disparity to gender discrimination and call for research aimed at evaluating the explanations.
The analysis should have been unexceptionable. Anyone who has fled a cluster of men at a party debating the fine points of flat-screen televisions can appreciate that fewer women than men might choose engineering, even in the absence of arbitrary barriers. (As one female social scientist noted in Science Magazine, "Reinventing the curriculum will not make me more interested in learning how my dishwasher works.") To what degree these and other differences originate in biology must be determined by research, not fatwa. History tells us that how much we want to believe a proposition is not a reliable guide as to whether it is true.
Nor is a better understanding of the causes of gender disparities inconsequential. Overestimating the extent of sex discrimination is not without costs. Unprejudiced people of both sexes who are responsible for hiring and promotion decisions may be falsely charged with sexism. Young women may be pressured into choosing lines of work they don't enjoy. Some proposed cures may do more harm than good; for example, gender quotas for grants could put deserving grantees under a cloud of suspicion, and forcing women onto all university committees would drag them from their labs into endless meetings. An exclusive focus on overt discrimination also diverts attention from policies that penalize women inadvertently because of the fact that, as the legal theorist Susan Estrich has put it, "Waiting for the connection between gender and parenting to be broken is waiting for Godot." A tenure clock that conflicts with women's biological clocks, and family-unfriendly demands like evening seminars and weekend retreats, are obvious examples. The regrettably low proportion of women who have received tenured job offers from Harvard during Summers's presidency may be an unintended consequence of his policy of granting tenure to scholars early in their careers, when women are more likely to be bearing the full burdens of parenthood.
Conservative columnists have had a field day pointing to the Harvard hullabaloo as a sign of runaway political correctness at elite universities. Indeed, the quality of discussion among the nation's leading scholars and pundits is not a pretty sight. Summers's critics have repeatedly mangled his suggestion that innate differences might be one cause of gender disparities (a suggestion that he drew partly from a literature review in my book, The Blank Slate) into the claim that they must be the only cause. And they have converted his suggestion that the statistical distributions of men's and women's abilities are not identical to the claim that all men are talented and all women are not—as if someone heard that women typically live longer than men and concluded that every woman lives longer than every man. Just as depressing is an apparent unfamiliarity with the rationale behind political equality, as when Hopkins sarcastically remarked that, if Summers were right, Harvard should amend its admissions policy, presumably to accept fewer women. This is a classic confusion between the factual claim that men and women are not indistinguishable and the moral claim that we ought to judge people by their individual merits rather than the statistics of their group.
Many of Summers's critics believe that talk of innate gender differences is a relic of Victorian pseudoscience, such as the old theory that cogitation harms women by diverting blood from their ovaries to their brains. In fact, much of the scientific literature has reported numerous statistical differences between men and women.As I noted in The Blank Slate, for instance, men are, on average, better at mental rotation and mathematical word problems; women are better at remembering locations and at mathematical calculation. Women match shapes more quickly, are better at reading faces, are better spellers, retrieve words more fluently, and have a better memory for verbal material. Men take greater risks and place a higher premium on status; women are more solicitous to their children.
Of course, just because men and women are different does not mean that the differences are triggered by genes. People develop their talents and personalities in response to their social milieu, which can change rapidly. So some of today's sex differences in cognition could be as culturally determined as sex differences in hair and clothing. But the belief, still popular among some academics (particularly outside the biological sciences), that children are born unisex and are molded into male and female roles by their parents and society is becoming less credible. Many sex differences are universal across cultures (the twentieth-century belief in sex-reversed tribes is as specious as the nineteenth-century belief in blood-deprived ovaries), and some are found in other primates. Men's and women's brains vary in numerous ways, including the receptors for sex hormones. Variations in these hormones, especially before birth, can exaggerate or minimize the typical male and female patterns in cognition and personality. Boys with defective genitals who are surgically feminized and raised as girls have been known to report feeling like they are trapped in the wrong body and to show characteristically male attitudes and interests. And a meta-analysis of 172 studies by psychologists Hugh Lytton and David Romney in 1991 found virtually no consistent difference in the way contemporary Americans socialize their sons and daughters. Regardless of whether it explains the gender disparity in science, the idea that some sex differences have biological roots cannot be dismissed as Neanderthal ignorance.
Since most sex differences are small and many favor women, they don't necessarily give an advantage to men in school or on the job. But Summers invoked yet another difference that may be more consequential.In many traits, men show greater variance than women, and are disproportionately found at both the low and high ends of the distribution. Boys are more likely to be learning disabled or retarded but also more likely to reach the top percentiles in assessments of mathematical ability, even though boys and girls are similar in the bulk of the bell curve. The pattern is readily explained by evolutionary biology. Since a male can have more offspring than a female—but also has a greater chance of being childless (the victims of other males who impregnate the available females)—natural selection favors a slightly more conservative and reliable baby-building process for females and a slightly more ambitious and error-prone process for males. That is because the advantage of an exceptional daughter (who still can have only as many children as a female can bear and nurse in a lifetime) would be canceled out by her unexceptional sisters, whereas an exceptional son who might sire several dozen grandchildren can more than make up for his dull childless brothers. One doesn't have to accept the evolutionary explanation to appreciate how greater male variability could explain, in part, why more men end up with extreme levels of achievement.
What are we to make of the breakdown of standards of intellectual discourse in this affair—the statistical innumeracy, the confusion of fairness with sameness, the refusal to glance at the scientific literature? It is not a disease of tenured radicals; comparable lapses can be found among the political right (just look at its treatment of evolution). Instead, we may be seeing the operation of a fascinating bit of human psychology.
The psychologist Philip Tetlock has argued that the mentality of taboo—the belief that certain ideas are so dangerous that it is sinful even to think them—is not a quirk of Polynesian culture or religious superstition but is ingrained into our moral sense. In 2000, he reported asking university students their opinions of unpopular but defensible proposals, such as allowing people to buy and sell organs or auctioning adoption licenses to the highest-bidding parents. He found that most of his respondents did not even try to refute the proposals but expressed shock and outrage at having been asked to entertain them. They refused to consider positive arguments for the proposals and sought to cleanse themselves by volunteering for campaigns to oppose them. Sound familiar?
The psychology of taboo is not completely irrational. In maintaining our most precious relationships, it is not enough to say and do the right thing. We have to show that our heart is in the right place and that we don't weigh the costs and benefits of selling out those who trust us. If someone offers to buy your child or your spouse or your vote, the appropriate response is not to think it over or to ask how much. The appropriate response is to refuse even to consider the possibility. Anything less emphatic would betray the awful truth that you don't understand what it means to be a genuine parent or spouse or citizen. (The logic of taboo underlies the horrific fascination of plots whose protagonists are agonized by unthinkable thoughts, such as Indecent Proposal and Sophie's Choice.) Sacred and tabooed beliefs also work as membership badges in coalitions. To believe something with a perfect faith, to be incapable of apostasy, is a sign of fidelity to the group and loyalty to the cause. Unfortunately, the psychology of taboo is incompatible with the ideal of scholarship, which is that any idea is worth thinking about, if only to determine whether it is wrong.
At some point in the history of the modern women's movement, the belief that men and women are psychologically indistinguishable became sacred. The reasons are understandable: Women really had been held back by bogus claims of essential differences. Now anyone who so much as raises the question of innate sex differences is seen as "not getting it" when it comes to equality between the sexes. The tragedy is that this mentality of taboo needlessly puts a laudable cause on a collision course with the findings of science and the spirit of free inquiry.
Steven Pinker is Johnstone Professor of Psychology at Harvard and the author of The Stuff of Thought.This article originally ran in the February 14, 2005, issue of the magazine.